Using J- and Ks-band imaging obtained as part of the IMACS Cluster Building Survey (ICBS), we measure Sersic indices for 2160 field and cluster galaxies at 0.31 < z < 0.54. Using both mass-and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously star-forming, starburst, and post-starburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously star-forming, as well as post-starburst and passive types, but not between starbursts and post-starbursts. These results independently support two conclusions presented in Paper II of this series: (1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor mergers; (2) starbursts and post-starbursts generally represent transient phases in the lives of "normal" star-forming and quiescent galaxies, respectively, originating from and returning to these systems in closed "recycling" loops. In this picture, spectroscopically identified post-starbursts constitute a minority of all recently terminated starbursts, largely ruling out the typical starburst as a quenching event in all but the densest environments.

We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 mu m] photometry to assemble a sample ofmassive (log(M-star/M-circle dot) similar to 11.0) and quenched (specific star formation rate < 0.01 Gyr-1) galaxies at z similar to 1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local universe, z similar to 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are well fitted with exponentially decreasing star formation histories and short star formation timescales (tau <= 100 Myr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 Gyr. In the (u - r)(0)-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the z similar to 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 Gyr) than the quenched galaxies off the RS (1.5 Gyr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at z similar to 1.5 to be < 43%. We speculate that the young quenched galaxies off the RS are in a transition phase between vigorous star formation at z > 2 and the z similar to 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z similar to 1.5 RS is of the order of similar to 1Gyr.

We present an analysis of the galaxy stellar mass function in different environments at intermediate redshift (0.3 <= z <= 0.8) for two mass-limited galaxy samples. We use the IMACS Cluster Building Survey (ICBS; M-* >= 10(10.5) M-circle dot) to study cluster, group and field galaxies at z = 0.3-0.45, and the ESO Distant Cluster Survey (EDisCS; M-* >= 10(10.2) M-circle dot) to investigate cluster and group galaxies at z = 0.4-0.8. Our analysis thus includes galaxies with masses reaching just below that of the Milky Way. Excluding the brightest cluster galaxies, we show that the shape of the mass distribution does not seem to depend on global environment, Our two main results are: (1) Galaxies in the virialised regions of clusters, in groups, and in the field follow similar mass distributions. (2) Comparing the ICBS and EDisCS mass functions to mass functions in the local universe, we detect evolution from z similar to 0.4-0.6 to z similar to 0.07 in the sense that the population of low-mass galaxies has grown with time with respect to the population of massive galaxies. This evolution is independent of environment, i.e., the same for clusters and the field. Furthermore, considering only cluster galaxies, we find that no differences can be detected in their mass functions either within the virialised regions, or when we compare galaxies inside and outside the virial radius. Finally, we find that red and blue galaxies have different mass functions. However, the shapes of the mass functions of blue and red galaxies do not seem to depend on their environment (clusters groups and the field).

We present near-infrared emission line counts and luminosity functions from the Hubble Space Telescope Wide Field Camera 3 Infrared Spectroscopic Parallels (WISP) program for 29 fields (0.037 deg(2)) observed using both the G102 and G141 grism. Altogether we identify 1048 emission line galaxies with observed equivalent widths greater than 40 angstrom, 467 of which have multiple detected emission lines. We use simulations to correct for significant (>20%) incompleteness introduced in part by the non-dithered, non-rotated nature of the grism parallels. The WISP survey is sensitive to fainter flux levels ((3-5) x 10(-17) erg s(-1) cm(-2)) than the future space near-infrared grism missions aimed at baryonic acoustic oscillation cosmology ((1-4) x 10(-16) erg s(-1) cm(-2)), allowing us to probe the fainter emission line galaxies that the shallower future surveys may miss. Cumulative number counts of 0.7 < z < 1.5 galaxies reach 10,000 deg(-2) above an H alpha flux of 2 x 10(-16) erg s(-1) cm(-2). H alpha-emitting galaxies with comparable [O III] flux are roughly five times less common than galaxies with just H alpha emission at those flux levels. Galaxies with low H alpha/[O III] ratios are very rare at the brighter fluxes that future near-infrared grism surveys will probe; our survey finds no galaxies with H alpha/[O III] < 0.95 that have H alpha flux greater than 3 x 10(-16) erg s(-1) cm(-2). Our H alpha luminosity function contains a comparable number density of faint line emitters to that found by the Near IR Camera and Multi-Object Spectrometer near-infrared grism surveys, but significantly fewer (factors of 3-4 less) high-luminosity emitters. We also find that our high-redshift (z = 0.9-1.5) counts are in agreement with the high-redshift (z = 1.47) narrowband H alpha survey of HiZELS (Sobral et al.), while our lower redshift luminosity function (z = 0.3-0.9) falls slightly below their z = 0.84 result. The evolution in both the H alpha luminosity function from z = 0.3-1.5 and the [O III] luminosity function from z = 0.7-2.3 is almost entirely in the L-star parameter, which steadily increases with redshift over those ranges.

The Grism Lens-Amplified Survey from Space (GLASS) is a Hubble Space Telescope (HST) Large Program, which will obtain 140 orbits of grism spectroscopy of the core and infall regions of 10 galaxy clusters, selected to be among the very best cosmic telescopes. Extensive HST imaging is available from many sources including the CLASH and Frontier Fields programs. We introduce the survey by analyzing spectra of faint multiply-imaged galaxies and z greater than or similar to 6 galaxy candidates obtained from the first 7 orbits out of 14 targeting the core of the Frontier Fields cluster MACSJ0717.5+3745. Using the G102 and G141 grisms to cover the wavelength range 0.8-1.7 mu m, we confirm four strongly lensed systems by detecting emission lines in each of the images. For the 9 z greater than or similar to 6 galaxy candidates clear from contamination, we do not detect any emission lines down to a 7 orbit 1 sigma noise level of similar to 5x10(-18) erg s(-1) cm(-2). Taking lensing magnification into account, our flux sensitivity reaches similar to 0.2-5x10(-18) erg s(-1)cm(-2). These limits over an uninterrupted wavelength range rule out the possibility that the high-z galaxy candidates are instead strong line emitters at lower redshift. These results show that by means of careful modeling of the background-and with the assistance of lensing magnification-interesting flux limits can be reached for large numbers of objects, avoiding pre-selection and the wavelength restrictions inherent to ground-based multi-slit spectroscopy. These observations confirm the power of slitless HST spectroscopy even in fields as crowded as a cluster core.

The Spitzer South Pole Telescope Deep Field (SSDF) is a wide-area survey using Spitzer's Infrared Array Camera (IRAC) to cover 94 deg(2) of extragalactic sky, making it the largest IRAC survey completed to date outside the Milky Way midplane. The SSDF is centered at (alpha, delta) = (23:30, -55:00), in a region that combines observations spanning a broad wavelength range from numerous facilities. These include millimeter imaging from the South Pole Telescope, far-infrared observations from Herschel/SPIRE, X-ray observations from the XMM XXL survey, near-infrared observations from the VISTA Hemisphere Survey, and radio-wavelength imaging from the Australia Telescope Compact Array, in a panchromatic project designed to address major outstanding questions surrounding galaxy clusters and the baryon budget. Here we describe the Spitzer/IRAC observations of the SSDF, including the survey design, observations, processing, source extraction, and publicly available data products. In particular, we present two band-merged catalogs, one for each of the two warm IRAC selection bands. They contain roughly 5.5 and 3.7 million distinct sources, the vast majority of which are galaxies, down to the SSDF 5 sigma sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 mu Jy) at 3.6 and 4.5 mu m, respectively.

Near infrared slitless spectroscopy with the Wide Field Camera 3, on board the Hubble Space Telescope, offers a unique opportunity to study low-mass galaxy populations at high redshift (z similar to 1-2). While most high-z surveys are biased toward massive galaxies, we are able to select sources via their emission lines that have very faint continua. We investigate the star formation rate (SFR)-stellar mass (M-star) relation for about 1000 emission line galaxies identified over a wide redshift range of 0.3 less than or similar to z less than or similar to 2.3. We use the Ha emission as an accurate SFR indicator and correct the broadband photometry for the strong nebular contribution to derive accurate stellar masses down to M-star similar to 10(7) M-circle dot. We focus here on a subsample of galaxies that show extremely strong emission lines (EELGs) with rest-frame equivalent widths ranging from 200 to 1500 A. This population consists of outliers to the normal SFR-M-star sequence with much higher specific SFRs (> 10 Gyr(-1)). While on-sequence galaxies follow continuous star formation processes, EELGs are thought to be caught during an extreme burst of star formation that can double their stellar mass in a period of less than 100 Myr. The contribution of the starburst population to the total star formation density appears to be larger than what has been reported for more massive galaxies in previous studies. In the complete mass range 8.2 < log(M-star/M-circle dot)< 10 and a SFR lower completeness limit of about 2 M-circle dot yr(-1) (10 M-circle dot yr-1) at z similar to 1 (z similar to 2), we find that starbursts having EWrest(H alpha) > 300, 200, and 100 angstrom contribute up to similar to 13%, 18%, and 34%, respectively, to the total SFR of emission-line-selected sample at z similar to 1-2. The comparison with samples of massive galaxies shows an increase in the contribution of starbursts toward lower masses.

We have learned much about galaxy evolution since z = 2, and something to even higher redshifts. How can it be that we know so little about the star formation histories (SFHs) of individual galaxies? Although great progress has been made accumulating huge samples with only rudimentary properties, progress in galaxy evolution means connecting what we've learned to detailed measurements of the life-histories of specific - not just representative - systems.